Apparatus for making strain gauges



Nov. 16, 1943. N, CONNER 2,334,668

APPARATUS FOR MAKING STRAIN GAUGES Fild March 2, 1942 2 Sheets-Sheet 1' WWMQ lNVENi'OR RALPH N. COHHER ATTORNEY I Nov. 16, 1943. R. N. CONNER APPARATUS FOR MAKING STRAIN GAUGES Filed March 2, 1942 2 Sheets-Sheet 2 INVENTOR :RALPH N. CQNHER ATTORNEY Patented Nov. 16, 1943 APPARATUS FOR. MAKING STRAIN GAUGES Ralph N. Conner, Berkeley, Calif., assignor to The Baldwin Locomotive Works, a corporation of Pennsylvania Application March 2,1942, Serial No. 433,042v

' 8 Claims. (01.14041) This invention relates to an improved apparatus for makingstrain gauges f the type em playing a fine Wire filament bonded throughout its length to a test member adapted to be variably strained and whose electrical resistance variesin accordance with changes of strain in the filament.

The gauge filament is preferably of extremely fine diameter such as of the approximate order of one to three thousandths of an inch in diameter and is made of any suitable materials well-known in the art, such as Advance, Constantan, Iso-elastic or other copper-nickel alloys. The composition of such materials and their change of electrical resistance for a given change of strain are all well known. The filament is preferably wound-in a predetermined manner on to the surface of a thin sheet of carrier medium, such as paper, and bonded thereto throughout the length of the filament by any suitable cement, such for example, as Glyptal, Duco household cement, de Kohtinsky cement, etc. This paper carrier and the filament bonded thereto constitute a unit which, in turn, is adapted to be cemented to the surface of a test body throughout the effective length of the filament.

It is an object ofmy invention to provide an improved apparatus for making gauges of the foregoing type so that they will have a high degree of accuracy and uniformity whereby they can be used in large numbers with dependable and consistent results.

Another object is to provide an improved apparatus that is readily adjustable for making gauges of difierent forms, such as different gauge lengths.

- A further object is to provide an improved apparatus in which the filament may be wound in a predetermined form and bonded to the strip of paper in a manner that is relatively simple, economical in construction, operation and maintenance and is conducive to rapid and consistent manufacture of the gauges.

Other objects and advantages will be more apparent to those skilled in the art from the following description of the accompanying drawings in which:

Fig. 1 is a diagrammatic side elevation of my improved apparatus partially shown in section by being taken substantially on the line l-l of Fig. 4;

Fig. 2 is a fragmentary plan view of a filament winding head and a cam for actuating the same;

Fig. 3 is a small view of the complete cam for actuating the winding head;

Fig. 4 is a transverse section taken substantially on the line 4--4 of Fig. 1;

. Fig. 5 is an enlarged section through a pin or post upon which the filament is wound; and

Fig. 6 is a fragmentary strip of paper'upon which a series of the gauges are wound.

In the particular embodiment of my invention shown herein for purposes of illustration, I employ a winding drum generally indicated at I comprising a cylinder 2 fixed to a rotatable shaft 3 which is journalled in any suitable bearings not shown. An annular member 4 is rotatably seated in a suitable annular recess 5 and normally held therein in fixed angular relation to the cylinder 2 by a keeper ring 6 through bolts 1 and 8. A series of axial guide rods 9 are secured in ring 4 and extend through suitable openings in a second annular ring I!) having threaded engagement H with the outer end of cylinder 2. A look nut I2 is adapted to hold the annular ring It] in a fixed angular position relative to cylinder 2.

The ring 10 is provided with a series of Winding pins or posts l4 spaced uniformly around the ring circumference while a similar series of winding pins l5 are mounted on ring 4, the pins 15 being staggered with respect to pins l4. At given intervals, depending upon the number of substantially parallel lengths of filaments that each gauge is to have, are a series of pins l6, Fig.

4. The relationship of all of the pins with respect to the windings is diagrammatically indiucated in Fig.6 in which it will be noted that pins l6 are substantially laterally offset with respect to pins I5 thereby causing a portion of the filament I! to extend out and around pin [6 to permit suitable heavy leads l8 to be soldered thereto.

Each of the Winding pins I4, l5 and I6 are retractable within their annular rings 4 and II), this being accomplished as seen in Fig. 5 by having each pin provided with an enlarged base l9 yieldably pressed by a spring 20 against a plug 21 threaded in an outer end of a chamber 22 in which the spring and base 19 are disposed. The pins are formed integrally with their bases l9 and slidably extend through the plugs 2|, thus permitting the pins to be easily depressed until they are flush with the periphery of the annular rings.

To wind the filament around the pins, I provide feeding means comprising a reciprocating winding head or shuttle generally indicated at 23 having a rod 24 axially slidably supported in a suitable stationary bracket 25 and carries at its outer end a hollow feeding tube-like portion 25. A spool of filamentwire 21 is suitably Journalled on a bracket 28 secured to and reciprocable with rod 24 whereby the filament can feed through a pair of rollers 29 and thence through the tubular passage 26 as the feeding tube moves back and forth. To move the feeding tube back and forth a spring 30 is mounted on a rod 3| and interposed between a suitable boss of stationary bracket 25 and a collar on the end of rod 3| thereby biasing rod 24 to the right. A cam 33, Fig. 3, of suitable configuration is'adapted to drivingly engage a suitable cam follower roller 34 journalled in the end of rod 24. The cam has one depression 35 of sufficient depth that it allows the spring 30 to move the feeding head far enough to the right so as to pass beyond pin IS. The other portions of the cam such as 36 are of less depth so as to allow the feeding tube to be moved to the right just beyond the gauge pins IS. The

, cam lobes are, of course, large enough so as to move the feeding tube 26 to the left past the pins I4.

When the feeding tube 26 has been moved just winding drum a distance equal to one winding pin whereupon cam 33 then moves the feeding tube in the reserve direction and so on back and forth.

After the filament I1 is wound on a series of pins in the manner shown in Fig. 6, it is then necessary to transfer this Winding. to a piece of paper and cement the same thereto. To accomplish this a roller 4| of either metal or rubber is suitably journalled to 'run substantially in tangential contact with the annular rings 4 and ID. A continuous web of. paper 42 is unwound from a roll 43 and passes around the lower peripheral portion of roller 4| and is then wound on to a suitable roll 44 placed a sufficient distance from the roll 4| to permit adequate drying of cement which is initially placed on the under side of web 42 by a cement roller 45 running in a bath of liquid cement 45. As the web 42 with cement on its under surface passes down into tangential contact with the winding drum the pins therein are successively depressed by engaging the paper and roll 4|, the pins receding against the action of their spring 20. The pins are, therefore, withdrawn from the reverse bends of the filament and simultaneously with such withdrawal the cement coat on the paper automatically bonds the filament to the paper ih.the precise initially wound position of the filament whereupon the strip of paper with the filament winding thereon moves away from the winding drum I thus permitting the winding-pins to move radially outward to their normal winding position. The paper now proceeds toward roll 44 and by the time it is reached the cement is fully dry. If it is necessary to add additional-bonding cement to the filament and paper this may be done either before or afterthe roll 4|.

. After the gauges are wound on to drum 44- the continuous strip of paper and filament may have I relatively heavy leads l8 soldered or otherwise electrically connected to the portions of the fllament l1 extended to pins |6 as shown in Fig. 6. Thereupon the gauges are separated by cutting longitudinally along a line 48 and transversely along lines 49. If desired or necessary, a second piece of paper 50 may .be used to. cover the filament and be firmly bonded thereto throughout its effective length. To do this the paper 50 maybe fed as a continuous strip from a suitable roll and this strip, together with web 42, passed between a pair of pressure rollers 5| and 52. The leads for the individual gauge filament may be soldered thereto before the covering strip 50 is applied, the covering strip beingslightly narrower than web 42 so that the outer ends of the leads are partially exposed.

To adjust the length of-the gauge, lock nut I2 is loosened and nuts 1 are removed whereupon cylinder 2 is rotated while rings 4 and I0 are manually held against rotation. The threads II will cause ring ID to move inwardly or outwardly as may b desired until the desired length of gauge is obtained. 4 Lock nuts l2 and screws 1 are then tightened and a new cam 33 is installed corresponding to the'new length of gauge.

Fromthe foregoing disclosure, it is seen that I have provided a very effective apparatus whereby a gauge filament may be wound in its desired form and effectively bonded to a carrier member, such as a piece ofthin paper, all as a continuous operation for producing highly uniform gauges. Thevarious elements automatically cooperate in a simple. positive and direct manner and in the specific aspect of the invention the filamentis pre-formed and then automatically transferred to a pre-cemented strip of paper. The gauges formed as a result of my improved apparatus provide a very simple and yet highly compact continuous gauge strip adapted to be severed in a manner to produce a plurality of gauges. My improved apparatus insures gauges that have a high degree of uniformity and therefore are adapted for use in large numbers with assurance of highly consistent results. It will of course be understood that various changes in details of construction and arrangement of parts may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. An apparatus for winding gauges of the type having a fine wire filament wound in a predetermined. manner, comprising a member having a series of pins thereon arranged in the form of the gauge to be wound,-a tube through which a filament passes for feeding the filament around said pins, means for effecting relative movement between said feeding tube and pins so as to wind the filament on said pins in said predetermined manner, and means whereby said pins are axially movable so as to be withdrawn from the filament after it is wound on said pins.

2. An apparatus for winding gauges of the type having a fine wire filament wound in a. predetermined manner, comprising a'rotatable winding drum having a series .of pins thereon arranged in the form of the gauge to be wound, a movable tubular member for feeding a filament between two adjacent pins of substantially equal length, means for effecting relative movement between said feeding head and pins so. as to wind the pins so as to wind the filament on said pins in said predetermined manner, means for passing a continuous strip of sheet material into tangential contact with said winding drum, and said winding pins being axially movable so as to be with drawn from the filament winding when said sheet material is brought into said tangential contactwith the winding drum whereby the filament winding is brought into supporting relation to'the sheet material while the filament winding remains wound on said pins in its said predetermined manner.

being so arranged that the filament windings are brought into substantially contiguous relation to said sheet while on said drum.

6. An apparatus for winding gauges of the type having a fine wire filament wound in a predetermined manner, comprising a winding drum having a plurality of circumferential rows of pins, alternately staggered with respect to each other, a filament feeding head; means for reciprocating said feeding head back and forth between said circumferential rows of staggered pins, means for partially rotating said winding drum at substantially the end of each reciprocating movement of 4. An apparatus for winding gauges of the type having a fine wire filament wound in a predetermined manner,'comprising a rotatable winding drum having a series of pins thereon arranged in the form of a gauge to be wound a movable head for feeding a filament, means for effecting relative movement between said feeding head and pins so as to wind the filament on said pins in said predetermined manner, means for pass a continuous strip of sheet material into tangential contact with said winding drum, said winding pins being axially movable so as to be withdrawn from the filament winding when said sheet material is brought into tangential contact with the winding drum whereby the filament winding is brought into supporting relation to the sheet material' while the filament winding remains wound on said pins in its said predetermined manner, and means for'applying a liquid cement to the side of said sheet material which comes into contact with said winding drum thereby to cause said filament winding to adhere to said sheet material when the winding is removed from said pins.

5. An apparatus for Winding gauges of the type having a fine 'wire filament wound in a predetermined manner, comprising a winding drum having a series of pins thereon arranged in the form of the gauge to be wound, means whereby a continuous sheet of material can be fed into peripheral contact with said winding drum, and

means for winding a filament on said pins, said pins and continuous sheet and winding means the feeding head thereby to move the head sufficiently so as to cause the filament to feed'between the next two adjacent pins during the next reciprocating movement of the feedin head, means whereby said pins are axially movable, a roller adapted to havepontact with the winding drum periphery, and means whereby sheet material may be fed between said roller and drum during which time said pins are moved axially.

7. An apparatus for winding gauges of the type having a fine wire filament wound in a predetermined manner, comprising a member having a series of gauge pins thereon arranged in the form of the gauge to be wound and also having additional pins around which the filament is adapted to be periodically extended to enable leads to be secured to the filament,-means for successively winding a'filament around said gauge said drum and displaced to one side of'one row of i said pins at points between what will constitute adjacent gauges, a movable head for feeding a filament around said pins, means for effecting relative movement between said feeding head and pins so as to wind the filament on the gauge pins in said predetermined manner and for periodically causing the filament to be extended around said extra pins to form a length of fila- 7 ment to which a lead may be connected, and

means whereby said pins are axially movable so as to be withdrawn from the filament after it is wound on said pin.

RALPH N. CONNER. 

